In recent printed matters, photographs, illustrations, and colors have been used in rapidly increasing amounts. There has been thus an increasing demand for coated papers year after year, which have a smooth coated layer as an ink-receiving layer on the surface thereof compared with uncoated printing papers. There has been also an increasing demand for papers having lighter weight while keeping traditional paper thickness and printing quality to follow a recent trend of reducing costs. For printing quality of a coated paper, smoothness of a coated layer thereof is important, and the coated paper is generally subjected to a treatment of surface-smoothing with a super calender, a soft nip calender, or the like. However, since the treatment increases smoothness of the surface by pressing the paper, the treatment simultaneously increases a density of the paper and reduces a thickness of the paper. If keeping the thickness, the coated paper will have an increased weight.
In response to these demands, a thick coated paper with a low density having high glossiness and smoothness has been developed. For example, disclosed methods include a method of coating a paper having 0.30 to 1.00 g/cm3 density with an organic polymer gel to form a dried film layer of the gel and coating the paper with a hydrophilic coating material (JP-A2007-107171), a method of subjecting a coated layer containing a copolymer latex having a specific glass transition temperature, an average particle diameter of 100 to 200 nm, and 30% by weight or more of styrene content to a flattening treatment with a heat calender under the condition of 3 to 8% by weight of moisture content of a coated paper on which the coated layer is formed (JP-A2006-188783), and a method of producing a coated paper having a coated layer of 1.5 to 10 g/m2 per side, including a smoothing treatment of a base paper having a water content of 2 to 8% by weight with a calendering apparatus composed of specific rolls before a coating apparatus (JP-A6-146197).